Tuesday, December 20, 2005
White Christmas? Hanukkah?
Matt Ross @ 1:00 AM
Forecast
Today will be sunny, but seasonably cool and breezy with highs around 40 degrees. Wednesday should be similar if not a bit cooler before a very brief warmup heading into the weekend. Friday looks like the best chance to crack the 50 degree mark for the first time since December 4th. Right now Christmas Eve and Christmas Day look to be in the 40s with perhaps some rain, and the slight possibility of a little snow. More on that below.
White Christmas and Cold Decembers
There is some debate as to what exactly is meant by the phrase, "White Christmas". I think the best definition is snow cover of at least one inch. Sorry guys, that patch of ice in the shady part of your backyard isn't going to cut it. The chances of a White Christmas in DC are about 15%. Even less than 15% is the chance that we actually receive accumulating snow on Christmas Eve or Christmas Day. Our record snowfall on Christmas day is 5.4" on Christmas, 1962. We last received snowfall on Christmas in 2002 when after an initial burst on the 24th changed to rain, we got 1-2" later on Christmas day as the rain changed over. That same storm crushed Interior Northeast and New England with heavy snow. This year we may see something similar to 2002, though the details are very sketchy. Absent an inch on Christmas Day this year, we won't officially have a White Christmas, or as mentioned above, Hanukkah, which happens to start sundown on the 25th this year.
The bigger story than the snow this year is the cold. So far through December 19th, 15 days have been below average, 3 days average, and just one day slightly above. Even if we were to average normal for the rest of the month, we would still have the 3rd coldest December in the last 30 years, and I believe we will average below normal for the rest of the month. We are almost certain to have the coldest December since 2000 and a Top 10 coldest at National Airport is well within reach. It will be interesting to see if December will end up being the coldest winter month. If so, it will be only the 4th time in the last 30 years(1989, 1997, 2000).
Near Whiteout Conditions Monday morning in Pulaski, New York as a narrow lake effect snow band off of Lake Ontario dumps nearly 2 feet in 10 hrs.
Snow Lover's Crystal Ball 
Next Chance of Snow: Saturday, December 24th - Sunday, December 25th
Probability: 15%
Potential Impact:
Commentary: We are still well off from this potential event, so confidence is very low. There is a rainmaker that will approach from the west on Christmas Eve and potentially spark a coastal storm on Christmas day. Right now this looks like a mostly or entirely rain event. However, enough cold air could be dragged down with the departing system to end the rain with a brief changeover to snow or some snowshowers on Christmas Day. Stay tuned for updates throughout the week, but don't get your hopes up.
Today will be sunny, but seasonably cool and breezy with highs around 40 degrees. Wednesday should be similar if not a bit cooler before a very brief warmup heading into the weekend. Friday looks like the best chance to crack the 50 degree mark for the first time since December 4th. Right now Christmas Eve and Christmas Day look to be in the 40s with perhaps some rain, and the slight possibility of a little snow. More on that below.
Image courtesy of Intellicast
White Christmas and Cold Decembers
There is some debate as to what exactly is meant by the phrase, "White Christmas". I think the best definition is snow cover of at least one inch. Sorry guys, that patch of ice in the shady part of your backyard isn't going to cut it. The chances of a White Christmas in DC are about 15%. Even less than 15% is the chance that we actually receive accumulating snow on Christmas Eve or Christmas Day. Our record snowfall on Christmas day is 5.4" on Christmas, 1962. We last received snowfall on Christmas in 2002 when after an initial burst on the 24th changed to rain, we got 1-2" later on Christmas day as the rain changed over. That same storm crushed Interior Northeast and New England with heavy snow. This year we may see something similar to 2002, though the details are very sketchy. Absent an inch on Christmas Day this year, we won't officially have a White Christmas, or as mentioned above, Hanukkah, which happens to start sundown on the 25th this year.
The bigger story than the snow this year is the cold. So far through December 19th, 15 days have been below average, 3 days average, and just one day slightly above. Even if we were to average normal for the rest of the month, we would still have the 3rd coldest December in the last 30 years, and I believe we will average below normal for the rest of the month. We are almost certain to have the coldest December since 2000 and a Top 10 coldest at National Airport is well within reach. It will be interesting to see if December will end up being the coldest winter month. If so, it will be only the 4th time in the last 30 years(1989, 1997, 2000).
Next Chance of Snow: Saturday, December 24th - Sunday, December 25th
Probability: 15%
Potential Impact:
Commentary: We are still well off from this potential event, so confidence is very low. There is a rainmaker that will approach from the west on Christmas Eve and potentially spark a coastal storm on Christmas day. Right now this looks like a mostly or entirely rain event. However, enough cold air could be dragged down with the departing system to end the rain with a brief changeover to snow or some snowshowers on Christmas Day. Stay tuned for updates throughout the week, but don't get your hopes up.
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